" I was afraid someone would say that."

Maybe I have been lucky .... only had to replace perhaps four master cylinders in my life... but the one that said in the instructions that it had to be bench bled... I had to take back off and do exactly that...

If you do bench bleed it... try to find some plugs the size of the lines which will be hooking to it when you install it... keeps you from introducing any air just from the fluid running out.

You may can " bench bleed " it yourself in the car if you make things sorta like the " drip " tube used for setting start of delivery for fuel on our engines... with the end of the tube going back into the top of the master cylinder resevoir. So when you push on the piston the fluid which comes out is recycled into the top of the master cylinder. A self recovery system.